干酪乳杆菌益在模拟人体肠道内生长情况的研究

本文模拟人体肠道特点,研究了益生菌——干酪乳杆菌（L.casei）在正常温度、正常胃酸情况、正常胆碱情况和蛋白小肽对干酪乳杆菌的菌数变化.发现干酪乳杆菌能在37℃恒温条件下,pH值3.0（人体正常胃液的pH值）和正常胆碱下生长,是一种良好的益生菌菌种。     

氧气对干酪乳杆菌生长和活力的影响

以静置培养为对照,通过振荡培养制造有氧环境,对干酪乳杆菌的生长曲线、菌体活力进行分析。研究发现在有氧条件下菌体生长受到抑制,菌体密度小于静置发酵,在4℃保存时的活力迅速下降,另外,有氧生长菌体对热、胆汁等条件的耐受性较差,在50℃处理4h导致菌体迅速死亡,在含有胆汁的培养基中,菌体生长几乎停滞。通过透射电镜观察发现有氧条件下菌体细胞壁发生破裂,菌体细胞质成分溶出,导致菌体死亡。因此,氧气对干酪乳杆菌的生长具有抑制作用,造成细胞损伤,导致菌体活力降低。     

干酪乳杆菌在山药基质中的生长代谢研究

为开发利用丰富的山药资源，作者利用乳酸茵制备了发酵山药饮料。本文探讨了干酪乳杆菌在山药基质中的生长代谢情况及发酵基质之储藏性能。实验结果显示，山药基质中的碳源可满足茵体的生长需要，发酵前后的氨基酸含量未见明显提高；干酪乳杆菌在山药基质中生长代时约为413min；发酵基质在4℃经30d储藏后仍维持了良好品质。     

瑞士乳杆菌与干酪乳杆菌在脱脂乳中发酵特性的研究

研究了瑞士乳杆菌(Lh134)和干酪乳杆菌(Lc134)单独与组合在脱脂乳中发酵32 h的pH、发酵乳酸度值、活菌数和氨基酸态氮变化.结果表明,Lh134在脱脂乳中发酵速度比Lc134快,Lh134和Lc134组合在脱脂乳中的发酵能力高过二者单株发酵,发酵结束时pH下降至3.90,发酵乳酸度达到281.30°T,活菌数...     

干酪乳杆菌对农家干酪抗氧化活性及在其模拟胃肠道中存活能力的研究

本研究利用向农家干酪加入干酪乳杆菌的方式,研究农家干酪的抗氧化活性及在模拟胃肠道中乳酸菌的存活能力。通过对DPPH自由基、羟自由基的清除的能力以及对铁的还原能力指标的测定,利用PH 4.6-SN及12%TCA-SN进行抗氧化活性分析。结果表明:在第30 d时,DPPH自由基的清除能力达到最高值,为316μM Trolox,还原能力为0.647;羟自由基的清除率在第25 d时最高达到54.38%,在第30 d时有所下降。在对第20 d的农家干酪的水溶性提取液的冷冻干燥粉进行抗氧化活性的评价时,抗氧化活性得到提高;综上所述,添加干酪乳杆菌的农家干酪在储藏期内抗氧化活性显著增强。选择第20 d的农家干酪进行模拟胃肠道的存活能力研究,发现活菌数降低了5 log_(10) cfu/g,最终为7 log_(10) cfu/g,可起到益生作用。因此,加入干酪乳杆菌显著提高农家干酪抗氧化活性,农家干酪可以起到益生作用。     

干酪乳杆菌LC-15的增菌培养基设计及生长动力学研究

对1株具有降胆固醇作用的干酪乳杆菌(Lactobacillus casei)LC-15的增殖培养基进行了筛选和优化,同时对其在分批培养时的生长动力学进行了研究。所得增菌培养基配方为0.1mol/L pH6.8的Na2HPO4-柠檬酸配制经蛋白酶预水解的10%脱脂乳冻干粉,再添加0.5%的葡萄糖,1.5%的胰蛋白胨,0.3%酵母浸膏,在此培养基中的最大菌数可达8.8×109cfu/mL,分别比MRS及脱脂复原乳中提高了1.35倍和0.75倍。得到的干酪乳杆菌在优化培养基中分批培养的生长动力学模型为:N(t)=3.4088/(1+e3.3560-0.3254t)。     

干酪乳杆菌发酵荔枝汁在模拟胃肠道中耐受能力及其抑菌性的研究

以干酪乳杆菌发酵荔枝汁为研究对象,在人工胃液、人工肠液环境下对干酪乳杆菌的存活性能进行研究;同时,采用琼脂扩散法,研究其对六种常见食源性致病菌(肠炎沙门氏菌、宋氏志贺氏菌、大肠埃希氏菌O157:H7、单增李斯特氏菌、金黄色葡萄球菌和阪崎肠杆菌)的抑菌性,以及探究酸和酶等因素对发酵液抑菌性的影响。结果表明:在模拟胃肠消化中,干酪乳杆菌在pH 1.5、pH 2.0、pH 3.0和pH 4.0的人工胃液中培养4 h后,活菌数分别达到了260 CFU/mL、8.63×107 CFU/m L、9.57×107 CFU/m L和1.15×108CFU/m L;在人工肠液中消化12 h后,活菌数均在107 CFU/m L以上。在抑菌试验中,经去酸、去过氧化氢和酶解等不同处理的发酵液对肠炎沙门氏菌等五种常见食源性致病菌具有明显的抑制效果,而对阪崎肠杆菌均未表现出抑制作用,其中胞外多糖、H2O2和蛋白肽类物质对五种常见的致病菌是主要的抑菌物质。研究结果为干酪乳杆菌发酵荔枝汁能否在胃肠道中发挥有益作用提供体外实验的理论依据以及在当地食品工业的开发应用提供科学依据。     

干酪乳杆菌高浓度培养的初步研究

通过选择不同中和剂调酸、补料培养等方法研究了干酪乳杆菌的高浓度培养条件.结果表明初始培养基不调酸,在培养过程中,采用饱和Ca(0H)2作为中和剂,通过调酸碱控制pH值在6.3～6.6之间,不进行补料培养,干酪乳杆菌菌数达到109/mL,可用于菌粉的干剂制造中.     

干酪乳杆菌发酵过程的研究

发酵过程中干酪乳杆菌(L.casei)经过约12h由迟滞期后进入对数期,并保持几何增长直至发酵终点(72h),终点活菌数为(2.21±0.14)×1012g-1。发酵开始pH值为6.42±0.05,发酵终点pH值降至3.7±0.01。pH值降到6.30±0.01时,黏度开始变大且在发酵后期处于稳定状态。发酵过程中发酵乳中的氨基酸态氮的质量浓度从(0.022±0.002)g/100mL升至(0.0389±0.0005)g/100mL。     

干酪乳杆菌粉末发酵剂的研制

研究了干酪乳杆菌粉末发酵剂的制备及活化的条件.将高浓度培养后的干酪乳杆菌离心浓缩,以10%脱脂乳加2.7%甘油作保护剂制成悬浮液后冷冻干燥,采用4%脱脂乳粉作为活化液,活化时间150min,在此条件下粉末发酵剂活化完全,活力恢复较好.     

VIABILITY OF BIFIDOBACTERIUM LA CTIS AND LACTOBACILL US ACIDOPHILUS IN MILK: SODIUM CHLORIDE CONCENTRATION AND STORAGE TEMPERATURE

The growth and viability of Bifidobacterium lactis and Lactobacillus acidophilus per se and for both strains as a coculture were studied in reconstituted skim milk so as to assess their dependence upon temperature (5, I0 and 15C), NaCl concentration (0, 0.51 and 1.03 mol L-'), and storage time (0–8 weeks). Cultures of B. lads exhibited no signijkant loss of viability either with increasing NaCl concentration or increasing storage temperature within the ranges studied On the other hand, viability of L. acidophilus decreased with increasing temperature and increasing NaCl concentration under similar conditions. When cocultured with L. acidophilus, B. lactis was signiJicantly less tolerant to higher NaCl levels and higher temperatures than when in pure culture, although rial numbers were still above the threshold required for commercial application. Coculturing with B. lactis had no detrimental effect on viability of L. acidophilus. A mechanistic model, which considers the behavior of the pure and mixed microbial populations is described by specijic death rates which vary with temperature following Arrhenius relationships) and NaCl levels following simple inhibition kinetics) in the milk medium. Activation energies for the death rates of B. lactis and L. acidophilus were 14 kcal mot' and 9–15 kcal mol-I, respectively.     

用于高速切削加工的磁力轴承主轴特性

介绍了用于高速切削加工的磁力轴承主轴的结构、刚性曲线及其耐磨损、低功耗、高精度、高速度等主要特性，并通过与传统的各类轴承主轴的比较，揭示出磁力轴承主轴的优良特性及其广阔的使用前景     

INVESTIGATION OF INHIBITORY EFFECTS OF SEVERAL COMBINATIONS OF SODIUM SALTS ON THE GROWTH OF LISTERIA MONOCYTOGENES AND SALMONELLA ENTERICA SEROTYPE ENTERITIDIS IN MINCED BEEF

Inhibition effects of several combinations of sodium lactate (SL), sodium acetate, sodium diacetate (SDA) on the growth of Listeria monocytogenes and Salmonella enterica serotype Enteritidis were investigated in minced beef. The samples inoculated with 4.60 log cfu/g of Salmonella enteritidis and 4.70 log cfu/g of L. monocytogenes were treated with sodium salts and their combinations and stored at 4C. Sodium salts decreased the growth rate of S. enterica serotype Enteritidis. Combinations of the salts were bactericidal to S. enterica serotype Enteritidis but the growth of L. monocytogenes was delayed only by using the combination of 2.5% SL and 0.2% SDA.     

桂林水热法合成红宝石与其它红宝石内部特征的鉴别

对桂林水热法合成红宝石的内部特征进行研究，并分析它与天然红宝石或其它方法合成的红宝石在内部鉴定特征上的区别。     

EFFECT OF ETHANOL VAPOR ON GROWTH AND TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM IN A HIGH MOISTURE BAKERY PRODUCT

To determine the effect of ethanol vapor on toxin production by Clostridium botulinum, studies were done in English style crumpets (a_w 0.990, pH 6.5) challenged with 500 spores/g C. botulinum types A and proteolytic B and packaged in high gas barrier bags [ethanol transmission rate (ETR) 0.21 g/m²/day @ 25 C]. Crumpets were packaged in air with either commercially available ethanol vapor generators (Ethicap® 2, 4 or 6G) or cotton wool pads saturated with 2, 4 or 6 g of 95% food grade ethanol and stored at 25C. Toxin was detected in all inoculated control crumpets (0% ethanol) after 5 days at ambient temperature (25C). Ethicap® 2G delayed toxicity for 10 days while complete inhibition (>21 days) was observed in all crumpets packaged with 4 or 6G Ethicap® or with 2, 4 or 6 g of ethanol per pad. However, all crumpets were overtly spoiled by this time. Both headspace ethanol and absorption of ethanol by crumpets increased as a function of Ethicap® size/weight of ethanol. Based on these preliminary studies, ethanol vapor would appear to be an effective additional barrier to control the growth and toxin production by C. botulinum in high moisture bakery products and ensure the safety of these products at ambient temperature.     

RECOVERY AND GROWTH OF SOME FOOD-BORNE PATHOGENS IN IRRADIATED LOW AND HIGH FAT FISH DURING STORAGE AT 2-4C

This report presents results of the investigations carried out to understand the role of fat levels in fish on postirradiation recovery/survival and growth of four pathogens generally encountered in seafoods. Fish of low [golden anchoy, (Coillia dussumierij, 0.39%] as well as high fat [Indian sardine , (Sardinella longiceps), 7.1 %] content (with endogenous biota were inoculated separately with cells of Listeria monocytogenes 036 , Yersinia enterocolitica 5692 , Bacillus cereus and Salmonella typhimurium; and irradiated at doses of 1 and 3 kGy. The number of viable organisms for each was monitored for two weeks at 2-4C on appropriate selective media. The four pathogens studied exhibited variation in their ability to recover from radiation damage as evidenced in terms of lag period; but their recovery and subsequent growth was not influenced by the fat levels offish. No increased growth of any of the pathogens tested was evidenced in irradiated fish, when compared with nonirradiated one .